Magnetically operated electric circuit control apparatus



MAGNETICALLY OPERATED ELECTRIC CIRCUIT CONTROL APPARATUS Filed July 12, 1962 SAFETY EONTROL I NVENTOR.

Q i J I am xsmam T 4 36' M M. TY

coNTROL BCU IT ATTORNEYS United States Patent 3,233 060 MAGNETICALLY OPERATED ELECTRIC CIRCUIT CONTROL APPARATUS George Wintriss, Carversville, Pa.

Filed July 12, 1962, Ser. No. 209,329 Claims. (Cl. 200-87) This invention relates to apparatus for closing and opening an electric circuit to detect the movement of a part that travels close to a magnetic-responsive portion of the circuit. In the preferred construction the invention relates to magnetic cam means for producing an electric signal that corresponds to the movement of a part of a machine into a certain position during a cycle of operation of the machine.

In the operation of high-speed machines, such as punch presses, there is not time enough for an operator to stop the machine in the event that a work piece fails to be dislodged from a die; and it is necessary to use automatic safety controls to protect the machines against damage to the dies as a result of irregularities in the operation of the apparatus.

It is an object of this invention to provide improved means for actuating safety controls; and more specifically, to provide a magnetic element that takes the place of conventional mechanical cams that open and close switches to send electric signals to a circuit in timed relation with the movement of a part of the machine and as an indicator of a particular portion of the cycle of operation of the machine.

Another object is to provide a magnetic cam, and lnore especially a rotary magnetic cam which has one or more horseshoe magnets located at predetermined angular locations around the circumference of a rotary element. Where two or more magnets are used, successive magnets are offset from one another to obtain a continuity of the flux field. In the preferred construction the magnets are connected to strips that are bent to the curvature of the rotary element, and the strip is then secured in position on the rotary element.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views:

FIGURE 1 is a diagrammatic view showing an electric circuit with a switch and magnetic cam means for opening and closing the switch;

FIGURE 2 is a plan view of the magnets and the mounting strip for the magnets shown in FIGURE 1;

FIGURES 3 and 4 are diagrammatic views showing the installation of the switch at right angles to the shaft that carries the magnetic cam;

FIGURES 5 and 6 are diagrammatic views, similar to FIGURES 3 and 4, but showing the switch located parallel to the shaft that carries the magnetic cam;

FIGURE 7 is a diagrammatic view showing the switch located at right angles to the direction of movement of a reciprocating cam; and

FIGURE 8 is a diagram showing the switch located parallel to the direction of travel of a reciprocating cam.

FIGURE 1 shows an electric circuit 10 containing a 3,233,060 Patented Feb. 1, 1966 safety controller 12 in series with an electric switch 14. The safety controller receives signals from the switch 14 and utilizes these signals in connection with apparatus for stopping a motor, or disengaging a clutch, or otherwise shutting down the operation of the machine in the event of irregularity in operation.

The signal indicating the irregular operation may be supplied in various ways and is often supplied by feelers which detect the dislodgemcnt of Work pieces from a die or the termination of stock feed, or by sensing elements which detect abnormal increases in pressure on a die part, or straining of a frame or linkage of a machine.

It is usual to employ a second signal which is supplied to the controller at a predetermined moment in the cycle of operation of the machine. It is the correlation of this signal with the one supplied by the irregular operation that determines whether the safety controller will stop the machine. For example, a signal may be supplied to the controller at a moment in the cycle just preceding the stripping of the Work piece from a die. If another signal is not supplied by the movement of the work piece within a given interval after the first signal, the controller will stop the machine since the indication is that the work piece was not removed from the die. There are many other combinations of signals and this invention is concerned only with apparatus for supplying the control signal which is in timed relation with the operation of the machine, i.e., the signal which indicates a particular movement in the cycle of the machine.

The switch 14 includes a housing 16 closed by end walls 18 and containing two leaf-spring contacts 20 and 22, both of which are made of ferrous material.

The spring contact 20 extends through the end wall 18 to a termnial 24 which connects with a conductor 26 leading to the safety controller 12. The other leaf-spring contact 22 extends through the end wall 18 to a terminal 27 which is connected with a power line 28.

The leaf-spring contacts 20 and 22 normally remain spaced from one another so that the switch is open. Whenever a magnet is brought close to the housing 16, which is preferably made of plastic or some non-magnetic metal, the magnetism causes the leaf-spring contacts 20 and 22 to bend toward the magnet and this brings the contacts 20 and 22 into positions where they touch each other and close the circuit through the switch.

FIGURE 1 also shows a magnetic cam 30 including a disc or a cylinder 32 supported by an axle 34 which rotates to move the periphery of the cylinder 32 past the side of the housing 16 of the switch 14. There are horseshoe magnets 36, 3-7 and 38 connected to the circumference of the cylinder 32 along an are indicated by the dimension arrow 40.

FIGURE 2 shows the preferred correlation of the magnets 36, 37 and 38. Each of these magnets is a horseshoe magnet with its pole pieces extending radially outward away from the axis of the cylinder 32. The successive magnets are staggered and located so that opposite poles of successive magnets overlap and this maintains a continuity of flux throughout the are 40 (FIGURE 1).

As the cylinder 32 rotates, the switch 14 Will he closed by the flux from the magnets 36, 37 and 38 during an angle of movement of the cam 30 of approximately 40. If a longer signal is desired, more magnets are located around the circumference of the cylinder 32. If signals are desired at different times during the cycle of the machine, then magnets are located at spaced positions around the circumference of the cylinder 32. Ordinarily, the cylinder 32 will make one revolution for each cycle of the machine; but if there is symmetry in the cycle, the cam may make multiple revolutions for each cycle.

In order to reduce the cost of the magnetic cam and to make possible the construction of cams of different diameters with some standardization of parts, the magnets 36, 37 and 38 are attached to a strip 44 of metal or other material which is stiflly flexible and which is initially in a flat condition.

Each of the magnets 36, 37 and 38 is attached to the strip 44 by a rivet 46; and the strip 44 is attached to the cylinder 32 by screws 48, at opposite ends of the strip 44, screwed into openings 50 drilled in the circumference of the cylinder 32.

By having each of the horseshoe magnets 36, 37 and 38 attached to the strip 44 by a single rivet 46 at the center of the magnet, the strip can bend to a sharp radius of curvature and move away from the edge portions of the magnets, as shown in FIGURE 1. The overlapping relation of the flat side faces of the pole pieces of the magnets 36, 37 and 38 makes the magnets hold each other against angular displacement about the rivets 46 in case any of these rivets becomes loose. Where only one magnet is attached to the strip 44, two rivets 46, spaced along the center line of the magnet, can be used, as in the case of the middle magnet 37 in FIGURE 2.

In the operation of the apparatus shown in FIGURE 1, the magnets 36, 37 and 38 have no influence on the switch 14 when in the solid-line position shown, or when in any other position which locates them at a distance from the side wall of the housing 16. As the magnetic cam 30 rotates and brings the magnets into the positions shown in dotted lines, the reflux from the magnets attracts the ferrous leaf-spring contacts and 22 to one side of the housing 16 and brings them into contact with one another, as previously explained.

FIGURES 3 and 4 show the switch 14 extending at right angles to the axis of the axle 34 which is driven from the machine 56.

FIGURES 5 and 6 show the way in which a magnetic cam can be used with the switch 14 extending parallel to the axle 34. Although the cam 30 could be used in FIGURES 5 and 6, it is preferable to use a magnetic cam 30' in which the magnets are located at right angles to the positions shown in FIGURES 14. FIGURES 5 and 6 show three magnets 36', 37' and 38 connected to a strip 44'. Successive magnets have corresponding pole faces at opposite sides of the cam.

FIGURE 7 shows a horseshoe magnet 60 attached to a strip 62 which is fastened by screws 64 to one end of a reciprocating plunger 66. The magnet 60 and plunger 66 are shown at one end of their stroke in FIGURE 7 and the direction of movement of the plunger 66 is indicated by the double-headed arrow 68. This plunger 66 preferably makes a complete stroke once for each cycle of the machine.

FIGURE 8 is a view similar to FIGURE 7 but with a magnet 60' on a strip 62' attached by screws 64' to a plunger 66' which reciprocates in directions indicated by the double-headed arrow 68'. This movement is parallel to the switch 14 and the plunger preferably makes one complete stroke for each cycle of operation of the machine. 1

If a longer period for the closed circuit is desired in FIGURE 8, additional magnets may be added to the strip 62, as in the constructions illustrated in FIGURES 1-5.

The preferred embodiment of the invention has been illustrated and described, but changes and modifications can be made and some features *canbeused in different combinations without departing from the invention as defined in the claims.

What is claimed is:

1. Electrical circuit control apparatus including two control elements, one of which is a reed switch having reed contacts enclosed within an elongated tube and extending in the direction of the longitudinal extent of the tube, and the other of which is a group of horseshoe magnets for actuating the switch, each horseshoe magnet having pole pieces spaced fi om one another by a gap across which the fiux passes, and means supporting one of the control elements and movable to produce relative movement of the magnets with respect to the tube in the direction of the extent of said gap between the pole pieces and along 'a path having at least a portion of its extent generally parallel to the longitudinal extent of the tube along and beyond, in both directions, the position at which each magnet is most elfective to operate the switch, said magnets of the group being oriented so that one pole piece of each magnet is a leading pole piece and the other is a trailing pole piece as the magnet moves along said path, the trailing pole piece of one magnet being of opposite polarity from the leading pole piece of the next successive magnet and spaced therefrom to leave a gap for a flux field between successive magnets.

2. Electric circuit control apparatus including two control elements, one of which is a reed switch having reed contacts enclosed within an elongated tube and extending in the direction of the longitudinal extent of the tube, and the other of which is a group of horseshoe magnets for actuating the switch, each horseshoe magnet having pole pieces spaced from one another by a gap across which the flux passes, and means supporting one of the control elements and movable to produce relative movement of the magnets with respect to the tube in the direction of the extent of said gap between the pole pieces and along a path having at least a portion of its extent generally parallel to the longitudinal extent of the tube along and beyond, in both directions, the position at which the magnet is most effective to operate the switch, the group of magnets including a first row of horseshoe magnets oriented so that one pole piece of each magnet is a leading pole piece and the other is a trailing pole piece as the magnet moves along said path, the trailing pole piece of one magnet being of opposite polarity from the leading pole piece of the next magnet of the first row and spaced therefrom to leave a gap for a flux field between successive magnets, and a second row of horseshoe magnets having at least one magnet therein which overlaps two successive magnets of the first row and which has a pole piece of opposite polarity alongside the trailing edge of the pole piece of a magnet of the first row and a pole piece of opposite polarity alongside of the l ading pole piece of the next successive magnet of the first row.

3. The electric circuit control apparatus including a cylindrical element having a circumferential surface, a plurality of permanent magnets secured to a strip and each of which has pole pieces, a means connecting the strip with the circumferential surface with the magnets located in a row extending circumferentially around the cylindrical element, and with the magnets oriented so that the spacing of the pole pieces of each magnet extends in the direction of the circumferential extent of the row.

4. The electric circuit control apparatus described in claim 3 with the magnets being a group of horseshoe magnets oriented so that one pole piece of each magnet is a leading pole piece and the other is a trailing pole piece as the magnet moves along a path, the trailing pole piece of one magnet being of opposite polarity from the leading pole piece of the next magnet and spaced there-' r m t l ave a g p for a flux field between successive magnets,

5. The electric circuit control apparatus described in claim 3 characterized by the magnets being in two rows and being horseshoe magnets oriented so that one pole piece-of each magnet is a leading pole piece and the other is a trailing pole piece as the magnet moves along a path, the trailing pole piece of one magnet being of opposite polarity from the leading pole piece of the next magnet of the first row and spaced therefrom to leave a gap for a flux field between the successive magnets, and at least one magnet in the second row including a horseshoe magnet that overlaps two successive horseshoe magnets of the first row that has a pole piece of opposite polarity along 'side the trailing pole piece of a magnet of the first row and a pole piece of opposite polarity alongside the first row.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS Great Britain.

BERNARD A. GILHEANY, Primary Examiner.

leadingpole piece of the next successive magnet of the 15 ROBERT K. SCHAEFER, Examiner. 

1. ELECTRICAL CIRCUIT CONTROL APPARATUS INCLUDING TWO CONTROL ELEMENTS, ONE OF WHICH IS A REED SWITCH HAVING REED CONTACTS ENCLOSED WITHIN AN ELONGATED TUBE AND EXTENDING IN THE DIRECTION OF THE LONGITUDINAL EXTENT OF THE TUBE, AND THE OTHER OF WHICH IS A GROUP OF HORSESHOE MAGNETS FOR ACTUATING THE SWITCH, EACH HORSESHOE MAGNET HAVING POLE PIECES SPACED FROM ONE ANOTHER BY A GAP ACROSS WHICH THE FLUX PASSES, AND MEANS SUPPORTING ONE OF THE CONTROL ELEMENTS AND MOVABLE TO PRODUCE RELATIVE MOVEMENT OF THE MAGNETS WITH RESPECT TO THE TUBE IN THE DIRECTION OF THE EXTENT OF SAID GAP BETWEEN THE POLE PIECES AND ALONG A PATH HAVING AT LEAST A PORTION OF ITS EXTENT GENERALLY PARALLEL TO THE LONGITUDINAL EXTENT OF THE TUBE ALONG AND BEYOND, IN BOTH DIRECTIONS, THE POSITION AT WHICH EACH MAGNET IS MOST EFFECTIVE TO OPERATE THE SWITCH, SAID MAGNETS OF THE GROUP BEING ORIENTED SO THAT ONE POLE PIECE OF EACH MAGNET IS A LEADING POLE PIECE AND THE OTHER IS A TRAILING POLE PIECE AS THE MAGNET MOVES ALONG SAID PATH, THE TRAILING POLE PIECE OF ONE MAGNET BEING OF OPPOSITE POLARITY FROM THE LEADING POLE PIECE OF THE NEXT SUCCESSIVE MAGNET AND SPACED THEREFROM TO LEAVE A GAP FOR A FLUX FIELD BETWEEN SUCCESSIVE MAGNETS. 